Uittreksel
Introduction
Attachment of enteric pathogens such as E. coli O157 onto fresh produce is a crucial first step for contamination to occur. Before contact with the plant surface, E. coli O157 can be present for some time in feces, sewage, soil or water. In the case of contaminated water, research has shown that survival of E. coli O157 in water could lead to starvation stress for the pathogen. This leads in turn to a rapid adjustment of its physiology by induction of stress responses and up-regulation of virulence expression. Interestingly, these events seem to be involved in bacterial attachment as well.
Purpose
The aim of this study is to better understand the effect of starvation stress on the attachment of E. coli O157 onto lettuce leaves.
Methods
E. coli O157 was introduced at 3 x 107 log CFU/ml into either sterile distilled water (SDW), phosphate buffered saline (PBS) or irrigation water (IW). The inocula were stored at 4°C and 20°C, and were used at days 0, 2 and 6 for an attachment assay on butterhead lettuce. The pathogen levels in the inocula were determined by the plating method and the live/dead-qPCR technique. By comparing both techniques, starvation stress could be estimated and correlated with the attachment ability of the pathogen.
Results
qPCR-data revealed a die-off of E. coli O157 only in IW stored at 20°C although a decrease in platecounts, an indicator of stress, was observed for most of the treatments. In general, the pathogens were least stressed in PBS and most stressed in IW. None of the treatments revealed an absolute increase in the number of attached E. coli O157 after 6 days (P > 0.05). However, when comparing plate counts, we observed a relative increase in function of time for IW and SDW.
Conclusions
Our study demonstrates that starvation in water could have an effect on E. coli O157 attachment onto butterhead lettuce. In future experiments, we will attempt to identify the underlying mechanisms of attachment; the results may contribute to designing more effective practices for prevention of fresh produce contamination.
Acknowledgments
This study was funded by the Federal Public Service of Health, Food Chain Safety and Environment (contract RF 6202).
| Oorspronkelijke taal | Engels |
|---|---|
| Titel | Proceedings of the European Symposium on Food Safety |
| Publicatiedatum | 2012 |
| Publicatiestatus | Gepubliceerd - 2012 |
| Evenement | International Association for Food Protection's Europan Sympsium on Food Safety 2012 - Warschau, Polen Duur: 21-mei-2012 → 23-mei-2012 http://www.foodprotection.org/europeansymposium/2012/ |